In many clinical situations it is necessary to ensure that a tubular organ will retain a diameter above a certain critical diameter. Such is the case, for example, where a coronary artery is expanded with an angioplasty catheter, in which case it is desired to prevent the expanded portion from being narrowed again. Another example is in the case of tracheal cancer, in which it is necessary to ensure that the trachea remains open in order to avoid suffocation.
Stents prepared by weaving a stainless steel wire in the form of a net has been proposed (Surgery, 1986, 99, 199-205). Another stent formed of a one-way shape memory allow was proposed in Japanese Published Application No. 61-6655. Such stents are introduced into a predetermined location in the tubular organ and then allowed to expand. However, such stents after once put in position are fixed and cannot be removed. This is a serious drawback in cases where the stent has to be removed or when the initial position of the stent is inaccurate and has to be improved. In all such cases, removal of the stent can cause serious injury to the tubular organ.
U.S. Pat. No. 5,037,427, discloses a stent made of a two-way shape memory alloy and means for its deployment in and recovery from a tubular organ. In accordance with this patent, the stent has a transition temperature which is below the body temperature in which it changes its diameter from a narrow diameter to a wide diameter in which it attaches to the walls of the tubular organ. The stent is inserted into the tubular organ under a constant flow of cold fluid and once the correct position of stent is reached, the flow of the cold fluid is stopped and the stent then expends under the influence of the body temperature. For removal, the stent is cooled again and withdrawn under a continuous application of a cold fluid. It will no doubt be appreciated that a continuous application of a cold fluid may not always be practical, and this is a continuous drawback for various applications.
It is the object of the present invention to provide a novel stent.
It is furthermore the object of the present invention to provide a stent which can easily be deployed and removed in a tubular organ.
It is furthermore the object in accordance with a preferred embodiment of the present invention to provide a stent which provides a constant pressure on the walls of a tubular organ.
It is still a further object of the present invention to provide means adapted for deployment and removal of the stent into and from a tubular organ.
The remaining object of the present invention will be realized from the following description.